1. Field of the Invention
This invention relates to a method and apparatus used to position a floating vessel so a to place the bow of the vessel into the direction of approaching waves. Orientation of the vessel in this manner reduces the risk of the vessel capsizing, reduces discomfort, fatigue, and risk of injury to the crew, and reduces the wave drift forces tending to move the vessel off location if the vessel is moored with multiple anchors or by dynamic positioning.
2. Description of the Prior Art
In a storm when waves become high enough even large ships must turn the bow into oncoming waves to reduce the risk of damage and the possibility of capsizing. This is true of ships traveling at sea from one point to another. It is also true with ships moored on a location such as drill ships, because with drill ships it is important even in lower sea states to point into the waves to reduce lateral movements of the ship which cause much discomfort, fatigue, and hazard to the crew involved in the drilling operation.
Waves that impact a ship at any angle except directly on the bow or stern cause lateral components of acceleration and vessel motion from yaw, sway, and roll. This lateral motion makes manual work most difficult; one must brace themselves strongly and move with the ship or walk from side to side to stay upright. Objects that are tied down strain their lashings and slide or roll and become dangerous if they break free. This lateral motion hampers crew operations, especially on vessels where manual labor must continue during adverse weather conditions, such as on offshore drilling vessels positioned over subsea wellheads. While various position control systems may be employed to maintain one of these drilling vessels over a subsea wellhead, such as the system described in U.S. Pat. No. 3,145,683, by H. L. Shatto, Jr. and R. H. Kolb entitled SHIP CONTROL SYSTEM, filed Aug. 22, 1961, Ser. No. 133,119, no means are provided to change the vessel heading to compensate for change in wave direction. It becomes very difficult at night or other times of poor visibility to tell which direction the waves that most affect the ship are coming from. An apparatus needs to be developed to allow a vessel's crew to determine which direction the vessel should be turned to in order to reduce lateral motions, and to minimize the risk of capsize of the vessel.